MANDELSON is the man who had to quit the cabinet twice and whose sudden return to the political front bench is perhaps the most spectacular comeback of all time.

I suppose that's politics. But, if ever there was a lesson Cameron needs to learn, it's that actions speak so much louder than words.

Throughout the expenses scandal, Cameron sought to become a paragon of virtue, a strong leader who made big promises about new politics and an open, transparent form of governance.

For a while, he was as good as his word. Tory MPs who failed to meet his standards over expenses soon found themselves out in the cold. Whether it was just a happy coincidence that many of these MPs were Tory old guard Cameron could happily manage without is something only those within the Tories can confirm.

But, throughout this time, the issue surrounding deputy chairman Lord Ashcroft's vague promise to become a British resident again after becoming a peer, had been bobbling along in the background.

Last week, as details of a Freedom of Information request came to light, Lord Ashcroft coughed to the fact he was still a non-dom, avoiding paying millions of pounds in tax to the country in which he seeks so much political influence. Ashcroft says that was always the plan, many in Parliament say it wasn't.

What I can't understand is why Cameron hasn't taken the same tough line with Lord Ashcroft as he did with MPs and their expenses. On one hand, he says he's all for legislation which forces all peers and MPs to be fully paid up citizens of the UK, but on the other is happy for his party deputy chairman to do the opposite.

If, as was suggested at the weekend, Lord Ashcroft's donations equate to just 1% of current earnings in the party, why doesn't Cameron get tough with him, too?

It's one thing to promise change, but quite another to deliver on that when it risks a battle within the party. At a time when many millions of voters are feeling under economic pressure, trying to wave away almost a decade of dodging over the tax status of a key Tory figure doesn't reflect well on the party.

The irony is that Lord Ashcroft has been most active in marginal seats – the very seats where the mystery over his tax status can now be used by political rivals to unpick the financial advantage his generous donations had given the chosen Tory candidates.

For Cameron, the lessons are clear. Simply making an announcement and telling everyone to move on isn't enough. It's arrogant and makes it look as if the party has something to hide. Which, in the case of Lord Ashcroft's tax status, it appears they had.